The present invention relates to a rubber composition for a side wall, assuming when petroleum depletes, and further relates to a rubber composition for a side wall having excellent strength and flex crack resistance.
As a rubber composition for the side wall of a tire, a butadiene rubber has been conventionally blended for improving the flex crack resistance in addition to a natural rubber exhibiting excellent tear strength, and further, carbon black has been used for improving weather resistance and reinforcing property.
However, environmental problems have been recently emphasized, and the regulation of CO2 discharge control has been enforced. Further, since petroleum raw material is finite, and its supply quantity has been reduced year by year, the enhancement of petroleum price is estimated in the future, and there is limit for using raw materials comprising petroleum resources such as a butadiene rubber and carbon black. Consequently, assuming a case where petroleum depletes in the future, it is necessary to use resources other than petroleum such as a natural rubber, and white fillers such as silica and calcium carbonate. However, in such case, there is required to have the same or more performances such as the flex crack resistance and reinforcing property than those which are obtained by the use of the conventionally used petroleum resources.
For example, JP-A-2003-63206 discloses technology which shows raw materials for a tire assuming when petroleum depletes, but the reference does not disclose a rubber composition for a tire side wall which exhibits adequate flex crack resistance and strength.